1. Field of the Invention
The present invention relates to a magnetic disk apparatus to be used in a data processor and, particularly, to a magnetic head positioner for a magnetic disk apparatus, which can prevent mechanical shock generated when an arm assembly collides with a stopper by erroneous operation or reckless run of the assembly from being transmitted to the magnetic head.
2. Description of the Related Art
In a conventional magnetic disk apparatus, a magnetic head is generally mounted on a rotary carriage. The magnetic head magnetically reads/writes information with respect to a recording surface of a magnetic disk medium which is rotating at high speed while being floated above the recording surface with a minute gap due to air pressure generated by the high speed rotation of the magnetic disk medium.
Further, servo information, that is, information for positioning the magnetic head at a predetermined location of the magnetic disk medium, is written in specific information recording areas of the magnetic disk medium. In the magnetic disk apparatus, the positioning of a data head with respect to a data recording area of the magnetic disk medium is performed based on the servo information. This system is referred to as a closed servo loop system. With this system, it becomes possible to perform a high speed positioning of the rotary carriage at the predetermined position on the magnetic disk medium.
Nowadays, seek time of a magnetic disk apparatus, that is, time necessary to move a magnetic head thereof to a predetermined location on a magnetic disk medium by driving a rotary carriage, of not more than 10 ms has been realized.
A magnetic head positioner for a conventional magnetic disk apparatus will be described with reference to FIG. 1.
In the magnetic head positioner for the conventional magnetic disk apparatus shown in FIG. 1, a plurality of magnetic disk media 1 are fixed to a spindle shaft 2 of a spindle motor (not shown) through a clamp ring 7 and a spindle hub (not shown). Opposite end portions of the shaft 2 are rotatably supported by base plates 3 provided within the magnetic disk apparatus through bearings (not shown), respectively. Thus, the plurality of the magnetic disk media 1 are rotatably supported within the magnetic disk apparatus.
On the other hand, a magnetic head 9 is provided correspondingly to each magnetic disk medium 1 for writing/reading information with respect thereto and the magnetic heads 9 are supported by front end portions of respective arm assemblies 12 so that they can be swung.
The arm assembly 12 is rotatably supported at a center portion thereof by a rotational shaft 13 through a bearing 14. The arm assembly 12 includes at a rear end portion a C shaped arm 50 and a coil 15 for rotationally driving the arm assembly 12 is fixed in a concave portion of the C shaped arm 50 by flexible adhesive 45.
A permanent magnet assembly 17 is arranged in a facing relation to the coil 15 in order that the arm assembly 12 is rotationally driven by torque generated by a magnetic circuit constituted by the coil 15 and the permanent magnet assembly 17. The permanent magnet assembly 17 is constituted basically by a permanent magnet and a yoke.
Each magnetic head 9 includes a servo head for reading out positioning information from a servo information recording surface of the magnetic disk medium 1 and a data head for reading/writing data with respect to a data recording surface of the magnetic disk medium 1. A data head of the uppermost magnetic head 9 is shown in FIG. 1.
It should be noted that the arm assembly 12 includes a servo arm (not shown) and a data arm (not shown) corresponding to the servo head and the data head, respectively.
A pair of stoppers 40 are provided outside the C shaped arm 50 with a predetermined distance therebetween. The stoppers 40 prevent the magnetic head 9 from being separated from the magnetic disk medium 1, even if the arm assembly 12 runs recklessly.
The magnetic head positioner of the conventional magnetic disk apparatus mentioned above, however, has problems to be described below.
In a normal operation, it is possible to accurately position the data head with respect to the magnetic disk medium based on the positioning information read out by the servo head, even if the seek operation for moving the arm assembly on which the magnetic head is mounted is performed at high speed. However, there may be an erroneous operation or reckless run of the arm assembly itself for some reason. In such case, when the C shaped arm collides with either stopper at a speed as high as about 1 to 3 m/s, the C shaped arm is subjected to a large collision deceleration, whereupon the coil fixed inside of the C shaped arm with adhesive is subjected to a large mechanical shock. The shock itself is absorbed by the adhesive to some extent.
However, when the operating speed of the arm assembly becomes about 2 to 3 m/s in the conventional magnetic head positioner, it becomes impossible to absorb such mechanical shock sufficiently even if the flexibility of the adhesive is very high and thus there is a possibility of damage of the coil adhered to the inside surface of the C shaped arm.
On the other hand, when the C shaped arm collides with either stopper at a speed as high as about 1 to 3 m/s, the C shaped arm is subjected to large collision deceleration which is transmitted to the magnetic head mounted on the front end portion of the arm assembly. As a result, the magnetic head vibrates, so that it becomes impossible to maintain a minute gap between the magnetic head and the magnetic disk medium constant. Therefore, the magnetic head is caused to repeatedly collide with the magnetic disk medium at high speed, leading to damage of the magnetic head itself or head crush.